Part IV. 



SYSTEMATIC SYNOPSIS 



OP THE 



FOSSIL BIRDS OF NORTH AMERICA. 



There is at present no satisfactory evidence that Birds existed in North America hcfi tc the 

 Jurassic period; the footprints in the sandstone of the Connecticut Valley attributed to Birds 

 having probably all been made I)y Dinosaurian Reptiles (p. 63). A unmher of C'retaeeons 

 Birds have been known for some years, as given in the original edition of this work (1872) ; 

 but it is only since 1881 that this class of vertebrates has been traced back to the Jurassic 

 by the discovery of Laopterijx priscus on a geologic horizon nearly that of tlie fitnioiis 

 Archceopteryx. 



The Tertiary Birds of North America belong to genera identical with, or nearly related 

 to, those now living (p. 64). The case is otherwise with the earlier forms from the Cretaceous 

 and the Jurassic, which represent different primary divisions of the class Aves (p. 237), com- 

 parable in taxonomic value to that one {Saurune) which is based upon the ArcluEopieryx, or 

 to those afforded by the Ratite and the Carinate birds respectively. Most of these fi.irras are 

 Odontornithes, or Birds with teeth; having the teeth implanted either in grooves (Odon- 

 tolcce), or in sockets {OdontotormcB) , as illustrated by the genera Hesperornis and Ichtliyornis 

 respectively. 



In the original edition of the Key these Cretaceous types were ranged with those from the 

 Tertiary, their characters not having been fully worked out at that time. They have since 

 become well known, through Professor Marsh's splendid restorations and illustrations, iu his 

 great work entitled ' Odontornithes' (4to, Washington and New Haven, ISSO). 



It is deemed advisable to present the Fossil Birds of North America under the three 

 categories of the Tertiary, the Cretaceous, and the Jurassic forms; the first-nameil being 

 ranged under the several orders to which they are supposed to belong, as described in this 

 work ; the remainder, with few exceptions, being Odontornithes. 



